Segment-local-functions NPM

Segment Local Functions (SLF == Sloth)

Enable development and testing of Segment functions locally and in your choice of TypeScript or JavaScript. Features

Develop in your choice of TypeScript or JavaScript
When choosing TypeScript, enable fully typed development against tracking plans
Debug your functions from within your IDE, including initiating source-function runs from external URL calls (to test against your actual service providers), or initiating destination-function runs from the Segment UI (to enable easy testing with events collected by Segment)
Test your functions locally (for automated unit/functional testing),
Deployment of functions

Requirements

Node v12 or above
AWS-SAM ()
(optional) TypeScript
(optional) Nodemon, for automatically updating debug/test environments on code change
(optional) Ngrok, for opening up a URL to your local machine so your function can be called by your service whilst tested locally.
(optional) Mocha, for running the tests (this is the default framework used, but any testing framework will work)

Quick Start

Install the command-line utility:

npm i -g segment-local-functions

Create a new folder for your new function

mkdir my-test-function
cd my-test-function

Initalise a new project (and see the Detailed Usage Guide below for details on the init wizard)

sloth init

Edit your function src/function.js (for JavaScript), or src/function.ts (for TypeScript)

Edit your tests src/tests/test.js (for JavaScript), or src/tests/test.ts (for TypeScript)

If using TypeScript, compile your code

tsc -p .

Launch the local instance ready for debugging your code (you may want to run this in a new terminal as it keeps control whilst it is running)

sloth debug

If using JavaScript, run your tests as follows:

mocha src/tests/test.js

Or if using TypeScript, run your tests as follows:

mocha out/tests/test.js

From within your IDE, launch a new debug session. If using Visual Studio Code, a debug launcher is set-up. Go to Debug and select "Debug Function".

If developing a source function, test your function directly against your provider. To do this, launch the Grok-tunnel:

sloth grok

Take note of the URL returned, and point your service to call to this endpoint.

If developing a destination function, test your function via the Segment UI, to enable testing against events collected within your workspace. Again, you'll need the Grok-tunnel (if not already running):

sloth grok

Go to your Segment Workspace, under Catalog -> Functions you'll see your function listed. Go into edit and run and events will be proxied to your local instance for debugging. Note: The Segment function will probably time-out and "fail" because it isn't actually running any code (it's just being used to forward events); this is expected behaviour

Finally, to run tests locally for automated testing, kill any currently running sloth debug instance, and instead launch a test instance:

sloth test

Now, when you run your tests, you won't have to launch a debug session from your IDE; instead everything will just run immediately.

When ready to deploy your code run:

sloth deploy

Or, if you choose the GitHub workflow integration, enable the actions in your target repository.

Finally, if you choose TypeScript and also provided a tracking plan to develop against, you can update the definition against the latest tracking plan by running